Technical Field
The present invention relates to an input circuit that receives a plurality of input signals.
Related Art
Input circuits that receive a plurality of input signals are well known. As disclosed, for example, in JP-A-2005-245053, such an input circuit receives a plurality of input signals as analog signals, converts the inputted analog signals to digital signals, and externally outputs the converted signals as AD (analog-to-digital) data signals.
Such an input circuit may sometimes cause a short-circuit fault between the input wirings or between the terminals through which input signals are inputted. Therefore, in order to constantly detect a short-circuit fault that would occur between the input wirings, the input circuit disclosed in JP-A-2005-245053 constantly makes a comparison as to whether or not the input signals are the same in line circuits, on the precondition that the characteristics of the signals inputted to one terminal should be different from those of the signals inputted to an adjacently located terminal.
Specifically, if there is no short-circuit fault, the signals inputted to one terminal are different from the signals inputted to an adjacently located terminal, but will be the same in the occurrence of a short-circuit fault. Accordingly, comparison of the input signals in the line circuits enables detection of the occurrence of a short-circuit fault.
On the other hand, there is a method of detecting the occurrence of a short-circuit fault with another signal terminal that can exhibit the same characteristics in a normal state. For example, this method uses a dual circuit having an input wiring that includes two lines to which the same input signals are inputted to constantly make a comparison as to whether the input signals are the same in the line circuits.
Specifically, if there is no short-circuit fault relative to other input signals, the input signals are the same in the dual circuit, but will be different in the occurrence of a short-circuit fault. Thus, comparison between the input signals in the dual circuit enables detection of the presence or absence of a short-circuit fault.
However, when a short-circuit fault is detected by using such a dual circuit, detection lines are required to be redundantly increased in addition to an originally required one line. Provision of such additional detection lines can complicate the circuit, and further, can increase the number of components, resultantly increasing cost incurred in manufacturing a product.